The present invention relates generally to lasers, and more particularly, to a distributed Talbot filter surface-emitting distributed feedback (DFB) laser that provides for radiation of in-phase energy modes.
There has been much interest in monolithic two-dimensional arrays of surface emitting diode lasers in recent years. Arrays using etched 45 degree mirrors and distributed Bragg reflector designs have been demonstrated that produced several watts of output power. For the most part, these arrays had to be operated in the pulsed mode due to high thermal resistance from a p-side up bonding configuration and the absence of effective heat sinking. Many applications of two-dimensional arrays will require either continuous wave (CW) or high duty cycle operation.
Recent publications have described how silicon microchannel heat sinks may be applied to both non-monolithic and monolithic arrays for CW operation. Arrays of surface emitting distributed feedback (SEDFB) lasers, in particular, offer the promise of reliable high-power CW operation due to their p-side down design.
When designing and constructing any laser, it is normally a design objective to provide for a laser that has relatively good far-field beam quality. Ideally, it is desirable to produce a laser that produces a single-lobed far-field beam pattern having a width comprised of only diffraction spreading. In general, diode lasers do not operate in this manner. Much of the research over the last 20 years relating to high power diode lasers has focused on designing and constructing arrays of lasers that produce improved far-field beam patterns.
Conventional semiconductor laser arrays employ a straight line stripe pattern. This stripe pattern is somewhat disadvantageous because undesirable out-of-phase radiating modes are produced by the laser array. However, it is more desirable to have an array that produces a preferred in-phase radiating mode, which results in a more desirable single-lobed far-field beam pattern.
Therefore, it is an objective of the present invention to provide a surface-emitting distributed feedback semiconductor laser that radiates energy in in-phase radiating modes.